Al Qaeda terrorists crash United Airlines Flight 175 into the World Trade Center's south tower at 9:03 a.m. on Sept. 11, 2001, about 17 minutes after other hijackers flew American Airlines Flight 11 into the north tower. (Getty Images/Spencer Platt)

Following the Sept. 11, 2001, terrorist attacks, the U.S. government created the Department of Homeland Security, giving it stepped-up power to shadow and detain terrorism suspects. Then-President George W. Bush credited these measures — and intelligence and military operations abroad — with preventing new attacks on U.S. soil in the nearly eight years since 9/11. But some intelligence experts argue that the new department failed to coordinate the nation's many turf-conscious intelligence agencies, and that continued U.S. military pressure has rendered Osama bin Laden's al Qaeda terrorist network incapable of mounting new attacks within the United States. Moreover, jihadist cells that have wreaked havoc in Europe lack counterparts in the U.S., where Muslims are far less alienated, experts say. Still, the danger of a new attack remains. According to an emerging school of thought, Americans should learn to live with the possibility of an eventual attack, rather than expecting government to eliminate all danger.